(The Conversation) – The Arctic has warmed nearly four times faster than the global average since 1979. Svalbard, an archipelago near the northeast coast of Greenland, is at the frontline of this climate change, warming up to seven times faster than the rest of the world.

More than half of Svalbard is covered by glaciers. If they were to completely melt tomorrow, the global sea level would rise by 1.7cm. Although this won’t happen overnight, glaciers in the Arctic are highly sensitive to even slight temperature increases.

To better understand glaciers in Svalbard and beyond, we used an AI model to analyse millions of satellite images from Svalbard over the past four decades. Our research is now published in Nature Communications, and shows these glaciers are shrinking faster than ever, in line with global warming.

Specifically, we looked at glaciers that drain directly into the ocean, what are known as “marine-terminating glaciers”. Most of Svalbard’s glaciers fit this category. They act as an ecological pump in the fjords they flow into by transferring nutrient-rich seawater to the ocean surface and can even change patterns of ocean circulation.

Where these glaciers meet the sea, they mainly lose mass through iceberg calving, a process in which large chunks of ice detach from the glacier and fall into the ocean. Understanding this process is key to accurately predicting future glacier mass loss, because calving can result in faster ice flow within the glacier and ultimately into the sea.

Despite its importance, understanding the glacier calving process has been a longstanding challenge in glaciology, as this process is difficult to observe, let alone accurately model. However, we can use the past to help us understand the future.

AI replaces painstaking human labour

When mapping the glacier calving front – the boundary between ice and ocean – traditionally human researchers painstakingly look through satellite imagery and make digital records. This process is highly labour-intensive, inefficient and particularly unreproducible as different people can spot different things even in the same satellite image. Given the number of satellite images available nowadays, we may not have the human resources to map every region for every year.

Photo by Chris-Håvard Berge on Unsplash

A novel way to tackle this problem is by using automated methods like artificial intelligence (AI), which can quickly identify glacier patterns across large areas. This is what we did in our new study, using AI to analyse millions of satellite images of 149 marine-terminating glaciers taken between 1985 and 2023. This meant we could examine the glacier retreats at unprecedented scale and scope.

Insights from 1985 to today

We found that the vast majority (91%) of marine-terminating glaciers across Svalbard have been shrinking significantly. We discovered a loss of more than 800km² of glacier since 1985, larger than the area of New York City, and equivalent to an annual loss of 24km² a year, almost twice the size of Heathrow airport in London.

The biggest spike was detected in 2016, when the calving rates doubled in response to periods of extreme warming. That year, Svalbard also had its wettest summer and autumn since 1955, including a record 42mm of rain in a single day in October. This was accompanied by unusually warm and ice-free seas.

How ocean warming triggers glacier calving

In addition to the long-term retreat, these glaciers also retreat in the summer and advance again in winter, often by several hundred metres. This can be greater than the changes from year to year.

We found that 62% of the glaciers in Svalbard experience these seasonal cycles. While this phenomenon is well documented across Greenland, it had previously only been observed for a handful of glaciers in Svalbard, primarily through manual digitisation.

We then compared these seasonal changes with seasonal variations in air and ocean temperature. We found that as the ocean warmed up in spring, the glacier retreated almost immediately. This was a nice demonstration of something scientists had long suspected: the seasonal ebbs and flows of these glaciers are caused by changes in ocean temperatures.

A global threat

Svalbard experiences frequent climate extremes due to its unique location in the Arctic yet close to the warm Atlantic water. Our findings indicate that marine-terminating glaciers are highly sensitive to climate extremes and the biggest retreat rates have occurred in recent years.

This same type of glaciers can be found across the Arctic and, in particular, around Greenland, the largest ice mass in the northern hemisphere. What happens to glaciers in Svalbard is likely to be repeated elsewhere.

If the current climate warming trend continues, these glaciers will retreat more rapidly, the sea level will rise, and millions of people in coastal areas worldwide will be endangered.

Tian Li, Senior Research Associate, Bristol Glaciology Centre, University of Bristol; Jonathan Bamber, Professor of Glaciology and Earth Observation, University of Bristol, and Konrad Heidler, Chair of Data Science in Earth Observation, Technical University of Munich

This article is republished from The Conversation under a Creative Commons license. Read the original article.

At the most northerly tip of the UK, looking north from the island of Muckle Flugga, Shetland, the cold wind whips up the sea and gannets dive.

While biodiversity loss in the Arctic Ocean may seem like a distant issue, the Shetland Islands lie further north than the Arctic Ocean’s southernmost waters.
The Arctic Circle is only 380 miles (610km) north of British waters – the same distance as London to Edinburgh by road.

Arctic wildlife is changing in ways that scientists like us don’t yet fully understand. Better protection for these species is urgently needed.

Establishing a new North Pole marine reserve where industrial activities such as shipping, oil and gas exploration and fishing are banned could provide an ocean sanctuary for wildlife.

Explorer-turned-conservationist Pen Hadow wants to create an internationally agreed marine reserve in the Central Arctic Ocean by 2037. He was the first person to trek solo from Canada to the geographic North Pole 21 years ago. The route he took in 2003 is no longer possible due to climate change.

In 2021, Hadow founded the 90 North Foundation, an environmental charity that is campaigning for a North Pole marine reserve to protect the Arctic’s peoples, its wildlife and its natural landscape.

Our team of marine researchers at the University of Exeter is collaborating with Hadow to explore how climate change will affect the ice and oceans in the Arctic and beyond.

Projected climate change poses great peril for wildlife such as polar bears and narwhals which are highly adapted to Arctic waters, relying on multi-year ice for foraging and breeding habitat.

So far, we have completed two ten-day surveys for whales and dolphins using both visual sightings and acoustic or sound monitoring underwater. We have also collected water samples to test for “environmental DNA” or eDNA. By filtering water and collecting small fragments of biological material, we can identity the presence of species by sequencing the trail they leave behind in the water in the form of fish scales, poo, skin or mucus, for example.

Once we have built a picture of where wildlife lives and how it moves about, changes in the Arctic ecosystem can be more easily monitored.

Arctic animals are also regularly spotted in British waters.

Ringed seals have been seen as far south as Cornwall. Beluga whales have been spotted off the coast of Shetland, and Atlantic white-sided and white-beaked dolphins frequently move between UK waters and the low Arctic. Bearded seals have been spotted in UK coastal waters, as have walrus and harp seals.

Brent geese, barnacle geese and pink-footed geese plus eider ducks, red knot, ringed plover and bar-tailed godwits all migrate between the Arctic and the UK. These birds breed in the Arctic and sub-Arctic, then overwinter in the UK and Ireland. These birds are particularly vulnerable because climate change is leading to wetter springs that can reduce their breeding success.

The wildlife living along UK’s shores is already changing as a result of climate change. Some species might expand their range northwards and this could further disrupt the Arctic ecosystem.

As well as monitoring wildlife, we are tracking the changing volume and routes of ships travelling through the Arctic Ocean. While our research is at an early stage, it’s already clear that industrial vessel activity in the Arctic Ocean is increasing as fishing vessels and cargo ships take advantage of the receding ice to make swifter routes across the globe.

The Arctic albedo

As the Arctic changes, the ramifications will be felt globally. The Earth’s northernmost white cap acts as a reflective shield against solar radiation. As the ice recedes, and the surface of the Earth darkens, so too does the planet’s in-built ability to reflect the sun’s warming rays.

Standing on a boat at the edge of the Arctic ice, we can see the powerful glow of sunlight reflecting from the icy surfaces. Any loss of this albedo (the ability of white ice to reflect sunlight and heat from the sun) triggers further warming, catalysing a negative feedback loop with profound implications. Rising temperatures can only be tackled by reducing greenhouse gas emissions.

Alongside this, we must protect the unique wildlife that have made the Arctic their home. A broad and encompassing approach to conservation of northern ecosystems could help limit the effects of human activities and the changing climate across the Arctic region and beyond. A well-connected global network of marine reserves that includes the Arctic Ocean is urgently needed.

Kirsten Freja Young, Senior Lecturer, Ecology, University of Exeter and Brendan Godley, Professor of Conservation Science, University of Exeter

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Featured image: Kirsten Young has been monitoring wildlife in the Arctic Ocean. Danielle Zalcman, CC BY-NC-ND.

(The Conversation) – A vast network of ocean currents nicknamed the “great global ocean conveyor belt” is slowing down. That’s a problem because this vital system redistributes heat around the world, influencing both temperatures and rainfall.

The Atlantic Meridional Overturning Circulation funnels heat northwards through the Atlantic Ocean and is crucial for controlling climate and marine ecosystems. It’s weaker now than at any other time in the past 1,000 years, and global warming could be to blame. But climate models have struggled to replicate the changes observed to date – until now.

Our modelling suggests the recent weakening of the oceanic circulation can potentially be explained if meltwater from the Greenland ice sheet and Canadian glaciers is taken into account.

Our results show the Atlantic overturning circulation is likely to become a third weaker than it was 70 years ago at 2°C of global warming. This would bring big changes to the climate and ecosystems, including faster warming in the southern hemisphere, harsher winters in Europe, and weakening of the northern hemisphere’s tropical monsoons. Our simulations also show such changes are likely to occur much sooner than others had suspected.

National Oceanography Center: “The Atlantic Meridional Overturning Circulation (AMOC): What Is It and Why Is It So Important?”

Changes in the Atlantic Meridional Overturning Circulation

The Atlantic ocean circulation has been monitored continuously since 2004. But a longer-term view is necessary to assess potential changes and their causes.

There are various ways to work out what was going before these measurements began. One technique is based on sediment analyses. These estimates suggest the Atlantic meridional circulation is the weakest it has been for the past millennium, and about 20% weaker since the middle of the 20th century.

Evidence suggests the Earth has already warmed 1.5ºC since the industrial revolution.

The rate of warming has been nearly four times faster over the Arctic in recent decades.

Meltwater weakens oceanic circulation patterns

High temperatures are melting Arctic sea ice, glaciers and the Greenland ice sheet.

Since 2002, Greenland lost 5,900 billion tonnes (gigatonnes) of ice. To put that into perspective, imagine if the whole state of New South Wales was covered in ice 8 metres thick.

This fresh meltwater flowing into the subarctic ocean is lighter than salty seawater. So less water descends to the ocean depths. This reduces the southward flow of deep and cold waters from the Atlantic. It also weakens the Gulf Stream, which is the main pathway of the northward return flow of warm waters at the surface.

The Gulf Stream is what gives Britain mild winters compared to other places at the same distance from the north pole such as Saint-Pierre and Miquelon in Canada.

Our new research shows meltwater from the Greenland ice sheet and Arctic glaciers in Canada is the missing piece in the climate puzzle.

When we factor this into simulations, using an Earth system model and a high-resolution ocean model, slowing of the oceanic circulation reflects reality.

Our research confirms the Atlantic overturning circulation has been slowing down since the middle of the 20th century. It also offers a glimpse of the future.

Connectivity in the Atlantic Ocean

Our new research also shows the North and South Atlantic oceans are more connected than previously thought.

The weakening of the overturning circulation over the past few decades has obscured the warming effect in the North Atlantic, leading to what’s been termed a “warming hole”.

When oceanic circulation is strong, there is a large transfer of heat to the North Atlantic. But weakening of the oceanic circulation means the surface of the ocean south of Greenland has warmed much less than the rest.

Reduced heat and salt transfer to the North Atlantic has meant more heat and salt accumulated in the South Atlantic. As a result, the temperature and salinity in the South Atlantic increased faster.

Our simulations show changes in the far North Atlantic are felt in the South Atlantic Ocean in less than two decades. This provides new observational evidence of the past century slow-down of the Atlantic overturning circulation.

What does the future hold?

The latest climate projections suggest the Atlantic overturning circulation will weaken by about 30% by 2060. But these estimates do not take into account the meltwater that runs into the subarctic ocean.

The Greenland ice sheet will continue melting over the coming century, possibly raising global sea level by about 10 cm. If this additional meltwater is included in climate projections, the overturning circulation will weaken faster. It could be 30% weaker by 2040. That’s 20 years earlier than initially projected.

Such a rapid decrease in the overturning circulation over coming decades will disrupt climate and ecosystems. Expect harsher winters in Europe, and drier conditions in the northern tropics. The southern hemisphere, including Australia and southern South America, may face warmer and wetter summers.

Our climate has changed dramatically over the past 20 years. More rapid melting of the ice sheets will accelerate further disruption of the climate system.

This means we have even less time to stabilise the climate. So it is imperative that humanity acts to reduce emissions as fast as possible.

Laurie Menviel, Post-doctoral Research Fellow, Climate Change Research Centre, UNSW Sydney and Gabriel Pontes, Post-doctoral Research Fellow, Climate Change Research Centre, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

(The Conversation) – The melting of one of North America’s largest icefields has accelerated and could soon reach an irreversible tipping point. That’s the conclusion of new research colleagues and I have published on the Juneau Icefield, which straddles the Alaska-Canada border near the Alaskan capital of Juneau.

In the summer of 2022, I skied across the flat, smooth and white plateau of the icefield, accompanied by other researchers, sliding in the tracks of the person in front of me under a hot sun. From that plateau, around 40 huge, interconnected glaciers descend towards the sea, with hundreds of smaller glaciers on the mountain peaks all around.

Our work, now published in Nature Communications, has shown that Juneau is an example of a climate “feedback” in action: as temperatures are rising, less and less snow is remaining through the summer (technically: the “end-of-summer snowline” is rising). This in turn leads to ice being exposed to sunshine and higher temperatures, which means more melt, less snow, and so on.

Like many Alaskan glaciers, Juneau’s are top-heavy, with lots of ice and snow at high altitudes above the end-of-summer snowline. This previously sustained the glacier tongues lower down. But when the end-of-summer snowline does creep up to the top plateau, then suddenly a large amount of a top-heavy glacier will be newly exposed to melting.

That’s what’s happening now, each summer, and the glaciers are melting much faster than before, causing the icefield to get thinner and thinner and the plateau to get lower and lower. Once a threshold is passed, these feedbacks can accelerate melt and drive a self-perpetuating loss of snow and ice which would continue even if the world were to stop warming.

Ice is melting faster than ever

Using satellites, photos and old piles of rocks, we were able to measure the ice loss across Juneau Icefield from the end of the last “Little Ice Age” (about 250 years ago) to the present day. We saw that the glaciers began shrinking after that cold period ended in about 1770. This ice loss remained constant until about 1979, when it accelerated. It accelerated again in 2010, doubling the previous rate. Glaciers there shrank five times faster between 2015 and 2019 than from 1979 to 1990.

Associated Press Video: “Melting of Alaska’s Juneau icefield accelerates, losing snow nearly 5 times faster than in the 1980s”

Our data shows that as the snow decreases and the summer melt season lengthens, the icefield is darkening. Fresh, white snow is very reflective, and much of that strong solar energy that we experienced in the summer of 2022 is reflected back into space. But the end of summer snowline is rising and is now often occurring right on the plateau of the Juneau Icefield, which means that older snow and glacier ice is being exposed to the sun. These slightly darker surfaces absorb more energy, increasing snow and ice melt.

As the plateau of the icefield thins, ice and snow reserves at higher altitudes are lost, and the surface of the plateau lowers. This will make it increasingly hard for the icefield to ever stabilise or even recover. That’s because warmer air at low elevations drives further melt, leading to an irreversible tipping point.

Longer-term data like these are critical to understand how glaciers behave, and the processes and tipping points that exist within individual glaciers. These complex processes make it difficult to predict how a glacier will behave in future.

The world’s hardest jigsaw

We used satellite records to reconstruct how big the glacier was and how it behaved, but this really limits us to the past 50 years. To go back further, we need different methods. To go back 250 years, we mapped the ridges of moraines, which are large piles of debris deposited at the glacier snout, and places where glaciers have scoured and polished the bedrock.

To check and build on our mapping, we spent two weeks on the icefield itself and two weeks in the rainforest below. We camped among the moraine ridges, suspending our food high in the air to keep it safe from bears, shouting to warn off the moose and bears as we bushwhacked through the rainforest, and battling mosquitoes thirsty for our blood.

We used aerial photographs to reconstruct the icefield in the 1940s and 1970s, in the era before readily available satellite imagery. These are high quality photos, but were taken before global positioning systems made it easy to locate exactly where they were taken.

A number also had some minor damage in the intervening years – some Sellotape, a tear, a thumb print. As a result, the individual images had to be stitched together to make a 3D picture of the whole icefield. It was all rather like doing the world’s hardest jigsaw puzzle.

Work like this is crucial as the world’s glaciers are melting fast – all together they are currently losing more mass than the Greenland or Antarctic ice sheets, and thinning rates of these glaciers worldwide has doubled over the past two decades.

Our longer time series shows just how stark this acceleration is. Understanding how and where “feedbacks” are making glaciers melt even faster is essential to make better predictions of future change in this important region

Bethan Davies, Senior Lecturer in Physical Geography, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dubai’s famous Palm Jumeirah is not the only man-made island to have emerged from the sea this century. Over the past 20 years, many islands have been built to accommodate both tourists and well-heeled residents – especially in the Arabian Gulf states and China.

In an era of sea-level rise and increased storm activity, new islands may seem a risky venture. Yet the desire for a sea view and to put blue water between yourself and the noise, traffic and crime of the mainland is keeping the market buoyant.

Residential artificial islands cater for the rich and have serious environmental consequences. But they ride high on big promises. How else to explain the continuing expansion of Eko Atlantic, a complex of islands sprouting off coastal Lagos in Nigeria?

Digital. “Artificial Islands.” Dream / Dreamland v. 3, 2024.

Construction firms broke ground on Eko Atlantic’s boulevards and high-rise apartments in 2009. The city government has recently announced five more artificial islands “to open up the city”, and claims that the new islands generate and attract wealth and have already created “30,000 direct new jobs”, mostly in construction and maintenance.

The fashion for island-building shows no signs of abating. But instead of an answer to the desperate need for new housing among people who are set to be displaced by rising seas, new islands are offering yet another distraction for the wealthy.

How to build an island

As research for my book The Age of Islands, I visited all sorts of new enclaves that have been reclaimed from the sea. I was amazed at how quickly they can be built. In shallow water, creating an island is not technically complex: usually, the sea bed across a wide area is hoovered up and ground down, then sprayed and pummelled into a stable base.

In Lagos, the Gulf states and other island-building hotspots like the shores of the Chinese island province of Hainan, developers know their creations must be defended from the sea. Nigeria has the Great Wall of Lagos, a sea barrier containing about 100,000 concrete blocks and rising nine metres above the sea, to protect Eko Atlantic. More modest structures are favoured elsewhere, usually in the form of artificial reefs that are dragged and dropped into place, creating a shield against surging seas.

Will any of this be enough? Such barriers provide enough protection long enough to make island-building an economic proposition. But this calculation misses something important: all these islands rely on the mainland – that’s where they get their energy, water and food. Lagos is a low-lying city and large parts are in danger of flooding. The boulevards of Eko Atlantic won’t look so chic if they are marooned.

Critics of new islands point to the havoc they cause to coastal and river systems, changing patterns of sediment deposition and erosion and creating silty, warm lagoons that turn living marine environments into dead zones.

This is one of the reasons the Chinese government intervened to halt island-building around Hainan. From its shores you can see 11 projects, some in full swing, most paused.

The world’s biggest and most spectacular new island, Ocean Flower, is found here. It is shaped like a lotus with scrolling leaves and is already crowded with apartment blocks and outlandish architecture, including European-style castles, grandiose hotels and amusement parks. The plan was to have 28 museums, 58 hotels and the world’s largest conference centre.

Even in the hyperbolic world of island building, it sounds extreme. The developer, Evergrande, is now in financial trouble and 39 residential towers on Ocean Flower have been deemed to have flouted environmental and planning regulations and ordered to be demolished.

Boom-and-bust cycles would appear to plague new islands. But these tales shouldn’t mislead us into thinking this is an ailing industry. The financial incentives remain enormous and island makers are an adaptive breed.

Floating for a few

Floating islands have come to the fore recently: anchored platforms whose construction does not involve scraping away the seabed, making them less disruptive to the marine environment.

Plans for floating cities keep bubbling up. One prospect, Green Float, led by the Japanese company Shimz, would be a floating Pacific city designed to float on the equator “just like a lily pad” and house 40,000 people.

Building on the high seas will always be challenging, so it’s no surprise that ventures closer to shore, such as the Floating City in the Maldives, have been the first to materialise. Floating City is slated as a 500-acre development with 5,000 low-rise homes for 20,000 people arranged in a coral-like scatter of closely connected islets. The first islands have already been towed into place.

The Dutch architect of the scheme, Koen Olthuis, hopes that the Floating City will not be the preserve of the rich (unlike the others I’ve mentioned). His vision is of ordinary Maldivians, having lost homes and livelihoods to rising seas, finding a safe anchorage in the Floating City.

But from what I’ve seen, the world of artificial islands caters to the few not the many. Island-building is led by private developers, not environmentalists – or even states. Foreigners are already being induced to buy into Floating City and told this will be their ticket to a Maldivian residence permit. The bond between wealth and island building will not be easily broken.

Alastair Bonnett, Professor of Geography, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

As much of the Great Lakes region experiences its warmest winter on record, and more record high temperatures are expected in Michigan, the National Oceanic and Atmospheric Administration (NOAA) has reported record low levels of ice coverage on the Great Lakes, amid a steady, decades-long decrease in coverage.

While ice coverage on the Great Lakes usually peaks in the late February to early March, NOAA began reporting daily record-lows for Great Lakes ice coverage on Feb. 8, through Feb. 15. While there was a brief spike above historic lows after Feb. 15, those numbers quickly neared and tied low ice-coverage records, with historical lows recorded on Feb. 27 and 28, Jennifer Day, director of communications for NOAA’s Great Lakes Environmental Research Laboratory said in an email.

Ice coverage on the individual lakes has followed similar patterns, with Lake Superior, Lake Michigan and Lake Huron recording historic low coverage for the date on Feb. 28, while ice concentration for Lake Erie sat at 0% and concentration on Lake Ontario sat at less than half a percent.

NOAA Great Lakes Environmental Research Laboratory Ice Coverage Chart for Feb. 29, 2024. | National Oceanic and Atmospheric Administration.

Ice concentration on Lake Superior sat at 1.74% on Wednesday, while NOAA recorded 3.6% concentration in Lake Michigan and 7.84% concentration in Lake Huron.

The total peak for ice concentration across the five lakes was recorded on Jan. 22, with 16% coverage. However, Lake Superior has since recorded a new maximum for the year on Feb.19, exceeding its January peak.

Ayumi Fujisaki-Manome, an associate researcher at the Cooperative Institute for Great Lakes Research told the Michigan Advance the lack of ice is the result of anomaly conditions overlaid on long term warming trends. Alongside El Niño conditions contributing to a warmer and wetter winter than normal, the North Atlantic Oscillation — which describes atmospheric pressure patterns — is in a positive phase, which prevents cold arctic air from coming down into the Great Lakes region.

Day noted that the strong El Niño coupled with a warm December and above average air and water temperatures throughout winter did not create the conditions needed for ice to develop.

Low ice was also recorded in 2020 and 2023, Day said, with the annual maximum coverage near 20%, compared to the long-term average of 53%.

However, NOAA has also recorded very high ice years in the previous decade, in 2014, 2015 and 2019.

“Even though there’s a decreasing trend in max ice (5%/decade), there is a great deal of year to year variability,” Day said.

Although there has been a long-term decline in Great Lakes Ice Coverage, predicting those fluctuations from year to year remains a big question for researchers, Fujisaki-Manome said.

While a lack of ice may bring disappointment for those looking to ice fish in the Great Lakes, or visit ice caves near the coast, the lack of ice coverage also carries concerns for shoreline conditions, lake effect weather, and for various animal species in and around the Great Lakes.

Ice coverage serves as a barrier, protecting coastlines from high winds, high waves and storm surges. Without that barrier there will be long-term impacts, such as shoreline erosion, Fujisaki-Manome said.

A lack of ice to protect from waves makes shorelines more susceptible to coastal flooding and creates a higher potential for storm damage to shoreline infrastructure, Day said.

Additionally, less ice and more open water is the perfect set up for a lake effect snowstorm or an ice storm, Fujisaki-Manome said.

During late fall and winter cold air flowing over the warm waters of the Great Lakes leads to the production of lake effect snow leading to increased snowfall in areas downwind from the lakes. This effect usually diminishes late into the winter season, as the formation of lake ice reduces the supply of warm and moist air in the atmosphere.

Thick, stable ice also protects fish eggs that are deposited nearshore in the fall and incubate over winter, Day said. Ice cover can help minimize the effect of waves that would dislodge or break apart eggs from species like lake whitefish or lake herring, she said.

Ice cover also affects winter fishery harvests, especially in bays, drowned river mouth lakes and nearshore areas, Day said. During cold winters when ice is thick and lasts three to four months, harvests for panfish, whitefish, bass, walleye and yellow perch are high, with low harvests when coverage is low and unstable.

It is unlikely that total ice coverage across the Great Lakes will exceed its January peak, Day said.

Significant ice growth is not expected over the coming weeks, and longer term temperature trend predictions indicate that ice levels across the Great Lakes will likely remain below average for the next several weeks, Day said.

Kyle Davidson

A heat wave in Greenland and a storm in Antarctica. These kinds of individual weather “events” are increasingly being supercharged by a warming climate. But despite being short-term events they can also have a much longer-term effect on the world’s largest ice sheets, and may even lead to tipping points being crossed in the polar regions.

We have just published research looking at these sudden changes in the ice sheets and how they may impact what we know about sea level rise. One reason this is so important is that the global sea level is predicted to rise by anywhere between 28 cm and 100cm by the year 2100, according to the IPCC. This is a huge range – 70 cm extra sea-level rise would affect many millions more people.

Partly this uncertainty is because we simply don’t know whether we’ll curb our emissions or continue with business as usual. But while possible social and economic changes are at least factored in to the above numbers, the IPCC acknowledges its estimate does not take into account deeply uncertain ice-sheet processes.

Sudden accelerations

The sea is rising for two main reasons. First, the water itself is very slightly expanding as it warms, with this process responsible for about a third of the total expected sea-level rise.

Second, the world’s largest ice sheets in Antarctica and Greenland are melting or sliding into the sea. As the ice sheets and glaciers respond relatively slowly, the sea will also continue to rise for centuries.

Photo by Cassie Matias on Unsplash

Scientists have long known that there is a potential for sudden accelerations in the rate at which ice is lost from Greenland and Antarctica which could cause considerably more sea-level rise: perhaps a metre or more in a century. Once started, this would be impossible to stop.

Although there is a lot of uncertainty over how likely this is, there is some evidence that it happened about 130,000 years ago, the last time global temperatures were anything close to the present day. We cannot discount the risk.

To improve predictions of rises in sea level we therefore need a clearer understanding of the Antarctic and Greenland ice sheets. In particular, we need to review if there are weather or climate changes that we can already identify that might lead to abrupt increases in the speed of mass loss.

Weather can have long-term effects

Our new study, involving an international team of 29 ice-sheet experts and published in the journal Nature Reviews Earth & Environment, reviews evidence gained from observational data, geological records, and computer model simulations.

We found several examples from the past few decades where weather “events” – a single storm, a heatwave – have led to important long-term changes.

The ice sheets are built from millennia of snowfall that gradually compresses and starts to flow towards the ocean. The ice sheets, like any glacier, respond to changes in the atmosphere and the ocean when the ice is in contact with sea water.

These changes could take place over a matter of hours or days or they may be long-term changes from months to years or thousands of years. And processes may interact with each other on different timescales, so that a glacier may gradually thin and weaken but remain stable until an abrupt short-term event pushes it over the edge and it rapidly collapses.

Because of these different timescales, we need to coordinate collecting and using more diverse types of data and knowledge.

Historically, we thought of ice sheets as slow-moving and delayed in their response to climate change. In contrast, our research found that these huge glacial ice masses respond in far quicker and more unexpected ways as the climate warms, similarly to the frequency and intensity of hurricanes and heatwaves responding to changes with the climate.

Ground and satellite observations show that sudden heatwaves and large storms can have long-lasting effects on ice sheets. For example a heatwave in July 2023 meant at one point 67% of the Greenland ice sheet surface was melting, compared with around 20% for average July conditions. In 2022 unusually warm rain fell on the Conger ice shelf in Antarctica, causing it to disappear almost overnight.

These weather-driven events have long “tails”. Ice sheets don’t follow a simple uniform response to climate warming when they melt or slide into the sea. Instead their changes are punctuated by short-term extremes.

For example, brief periods of melting in Greenland can melt far more ice and snow than is replaced the following winter. Or the catastrophic break-up of ice shelves along the Antarctic coast can rapidly unplug much larger amounts of ice from further inland.

Failing to adequately account for this short-term variability might mean we underestimate how much ice will be lost in future.

What happens next

Scientists must prioritise research on ice-sheet variability. This means better ice-sheet and ocean monitoring systems that can capture the effects of short but extreme weather events.

This will come from new satellites as well as field data. We’ll also need better computer models of how ice sheets will respond to climate change. Fortunately there are already some promising global collaborative initiatives.

We don’t know exactly how much the global sea level is going to rise some decades in advance, but understanding more about the ice sheets will help to refine our predictions.

Edward Hanna, Professor of Climate Science and Meteorology, University of Lincoln and Ruth Mottram, Climate Scientist, National Centre for Climate Research, Danish Meteorological Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “The Day After Tomorrow” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.

While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?

Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium. Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.

In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.

The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.

We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.

The ocean’s conveyor belt

Ocean currents are driven by winds, tides and water density differences.

In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.

This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt.

Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt. A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point, it shuts down quickly.

What happens to the climate at the tipping point?

The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s. Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.

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This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.

We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.

The result: Dangerous cold in the North

Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.

The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent changed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.

These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.

The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points. For example, the Amazon rainforest is vulnerable to declining precipitation. If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.

The Atlantic circulation has slowed significantly in the distant past. During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.

So, when will we see this tipping point?

The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point, possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.

Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.

The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.

It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.

This article was updated on Feb. 11, 2024, to fix a typo: The experiment found temperatures in parts of Europe changed by more than 5 F per decade.

René van Westen, Postdoctoral Researcher in Climate Physics, Utrecht University; Henk A. Dijkstra, Professor of Physics, Utrecht University, and Michael Kliphuis, Climate Model Specialist, Utrecht University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

(The Conversation) – While the Southern Ocean around Antarctica has been warming for decades, the annual extent of winter sea ice seemed relatively stable – compared to the Arctic. In some areas Antarctic sea ice was even increasing.

That was until 2016, when everything changed. The annual extent of winter sea ice stopped increasing. Now we have had two years of record lows.

In 2018 the international scientific community agreed to produce the first marine ecosystem assessment for the Southern Ocean. We modelled the assessment process on a working group of the Intergovernmental Panel on Climate Change (IPCC). So the resulting “summary for policymakers” being released today is like an IPCC report for the Southern Ocean.

This report can now be used to guide decision-making for the protection and conservation of this vital region and the diversity of life it contains.

Why should we care about sea ice?

Sea ice is to life in the Southern Ocean as soil is to a forest. It is the foundation for Antarctic marine ecosystems.

Less sea ice is a danger to all wildlife – from krill to emperor penguins and whales.

The sea ice zone provides essential food and safe-keeping to young Antarctic krill and small fish, and seeds the expansive growth of phytoplankton in spring, nourishing the entire food web. It is a platform upon which penguins breed, seals rest, and around which whales feed.

The international bodies that manage Antarctica and the Southern Ocean under the Antarctic Treaty System urgently need better information on marine ecosystems. Our report helps fill this gap by systematically identifying options for managers to maximise the resilience of Southern Ocean ecosystems in a changing world.

An open and collaborative process

We sought input from a wide range of people across the entire Southern Ocean science community.

We sought to answer questions about the state of the whole Southern Ocean system – with an eye on the past, present and future.

Our team comprised 205 authors from 19 countries. They authored 24 peer-reviewed papers. We then distilled the findings from these papers into our summmary for policymakers.

We deliberately modelled the multi-disciplinary assessment process on a working group of the IPCC to distill the science into an easy-to-read and concise narrative for politicians and the general public alike. It provides a community assessment of levels of certainty around what we know.

We hope this “sea change” summary sets a new benchmark for translating marine research into policy responses.

So what’s in the report?

Southern Ocean habitats, from the ice at the surface to the bottom of the deep sea, are changing. The warming of the ocean, decline in sea ice, melting of glaciers, collapse of ice shelves, changes in acidity, and direct human activities such as fishing, are all impacting different parts of the ocean and their inhabitants.

These organisms, from microscopic plants to whales, face a changing and challenging future. Important foundation species such as Antarctic krill are likely to decline with consequences for the whole ecosystem.

The assessment stresses climate change is the most significant driver of species and ecosystem change in the Southern Ocean and coastal Antarctica. It calls for urgent action to curb global heating and ocean acidification.

It reveals an urgent need for international investment in sustained, year-round and ocean-wide scientific assessment and observations of the health of the ocean.

We also need to develop better integrated models of how individual changes in species along with human impacts will translate to system-level change in the different food webs, communities and species.

What’s next?

Our report was tabled at an international meeting of the Commission for the Conservation of Antarctic Marine Living Resources in Hobart.

The commission is the international body responsible for the conservation of marine ecosystems in the Southern Ocean, with membership of 26 nations and the European Union.

It is but one of the bodies our new report can assist. Currently assessments of change in habitats, species and food webs in the Southern Ocean are compiled separately for at least ten different international organisations or processes.

The Southern Ocean is a crucial life-support system, not just for Antarctica but for the entire planet. So many other bodies will need the information we produced for decision-making in this critical decade for action on climate, including the IPCC itself.

Beyond the science, the assessment team has delivered important lessons about how coordinated, collaborative and consultative approaches can deliver ecosystem information into policymaking. Our first assessment has taken five years, but this is just the beginning. Now we’re up and running, we can continue to support evidence-based conservation of Southern Ocean ecosystems into the future.

Andrew J Constable, Adviser, Antarctica and Marine Systems, Science & Policy, University of Tasmania and Jess Melbourne-Thomas, Transdisciplinary Researcher & Knowledge Broker, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Featured Image: Courtesy Pat James, Australian Antarctic Division.